1. Field of the Invention
The present invention relates to an improved interlocking nail geometry and method for use; and more particularly to an interlocking nail having an hourglass-shaped construction with an optional self-tapping tapered locking design.
2. Description of the Prior Art
Animals and humans often suffer from long bone fractures, such as fractures of the femur, tibia and humerus, which require medical intervention for stabilization. Surgery is generally required and involves implantation of devices appointed to provide stability for bone healing. Reconstruction of long bone fractures is generally achieved utilizing various implant devices currently available in human and veterinary fields. Varying levels of success are achieved through use of these conventional orthopedic devices based on their ability to stabilize the fracture and promote bone healing.
Non-stability at the fracture site can result in delayed healing and, in some cases, non-union of the fracture, thereby requiring revision surgery. In the latter scenario, fibrous tissue grows at the fracture site instead of bone, creating an unstable, painful limb. Non-union cases require revision surgery using combinations of these devices, i.e., interlocking nails in adjunct with an external fixator device. The common basis for resolving non-stability problems is to establish adequate resistance to bending and torsion through these device reconstructions, thereby preventing excessive motion at the fracture site and allowing the bone to bridge.
Orthopedic devices currently utilized involve combinations of implant devices, including: (i) external fixation devices with pins; (ii) bone plates and screws; and (iii) interlocking nails and transverse bolts or screws. (See FIGS. 1a, 1b, and 1c herein).
External fixation devices frequently fail to provide the requisite stability for proper bone healing, making use of these devices undesirable. Problems with external fixation devices occur not only from stability, but are also due to infection, as the pins used to stabilize the fragments extend through the skin into the bone, resulting in potential pathways for bacteria. Stability can be provided utilizing bone plates and screws, implantation of these devices requires invasive surgical procedures. Interlocking nails heretofore disclosed and utilized provide a less invasive approach than the bone plates and screws. However most designs of these devices do not provide adequate resistance to bending and torsion, and result in delayed union or non-unions due to micromotion of the construct.
Current interlocking nails are inadequate in achieving stability due to the nail geometry and the fit between the screw and the nail. Most nails are a straight rod design of consistent cross section, which creates higher stresses at the proximal and distal portions of the nail challenging the fixation. If these fracture fixation issues can be resolved, interlocking nails have the potential to provide a less invasive surgical approach and yield proper bone stabilization to promote healing.
Notwithstanding the efforts of prior art workers to construct an efficient interlocking nail that stabilizes bone fractures and promotes healing, there remains a need in the art for an interlocking nail having a geometry that promotes stability and, at the same time, requires less invasive surgical implantation. In addition, there is a need in the art for an interlocking nail having an hour-glass geometry and an optional rounded entry tip. Further, there is an art-recognized need for an interlocking nail having an hour-glass geometry and fixation holes provided with a self-tapping, tapered, locking design.